KANDAHAR, Afghanistan -- The carnage in Afghanistan continued unabated on a major Muslim holiday on Sunday, as attackers killed two pairs of brothers with links to the government and three NATO service members.

The targeted killings are part of a spate of similar attacks on those associated with the government, further complicating efforts by international forces in country to hand over security responsibility to Afghans as foreign combat troops withdraw.

In the first attack, a bomb hidden in a cemetery in the southern province of Helmand killed a police chief and his brother who were visiting a family grave for the Eid al-Fitr holiday.

Seven of the men's family members were wounded in the early-morning blast in the provincial capital of Lashkar Gah, said Helmand Deputy Police Chief Ghulam Rabbani.

No one immediately claimed responsibility, but the attack was consistent with the Taliban's strategy to target authorities and others who align themselves with the government or international forces.

The two men were brothers of a lawmaker for Helmand province, Abdulwadood Popal, who was not at the cemetery at the time of the blast. The family was visiting the grave after morning prayers for the holiday, which ends the month-long Ramadan fasting period.

Then in Farah province in the west, gunmen on a motorcycle opened fire on the car of an intelligence service official as he was driving home from a family visit, killing him and his brother who worked for the customs service.

Meanwhile in the east, NATO forces said that three international service members were killed in a bomb attack, without providing further details. At least 41 international troops have been killed so far this month in Afghanistan.

In a speech marking the holiday, President Hamid Karzai condemned the repeated insurgent attacks that took place during Ramadan.

"The enemies of Muslims ... during the holy month of Ramadan treated the nation of Afghanistan cruelly: bombs, explosions in mosques, suicide attacks in mosques," Karzai said.

If the Taliban were not responsible for such attacks, he said, they must disavow them.

"If you are not behind this, it is being done in your name. As Muslims, as Afghans, raise your voice and say that you did not do it," he appealed.

In a message ahead of Eid al-Fitr, Taliban leader Mullah Mohammad Omar instructed his fighters once again to avoid killing or wounding Afghan civilians.

"Employ tactics that do not cause harm to the life and property of the common countrymen," he said in an eight-page message released to news organizations last week. The Taliban have said previously, however, that they do not consider those who collaborate with the government to be civilians.

Targeted killings of Afghan civilians have surged this year, according to the United Nations. Civilian deaths from targeted killings and assassinations jumped 34 percent for the first six months of 2012 to 255 killed, from 190 in 2011, the U.N. said in a report issued earlier this month.

The U.N. report said 1,145 civilians were killed and 1,954 injured during the first half of the year, most of them by militants.

Also on Sunday, officials said that an airstrike by coalition forces in the northeast killed a large group of Taliban fighters and a local insurgent leader. At least two dozen insurgents were killed in the attack in Kunar province, said NATO forces spokesman Maj. Martyn Crighton.

Kunar Gov. Sayed Fazlullah Wahidi said the strike killed as many as 50 insurgents who had massed in a remote area of the province. He said it was not clear why they had gathered.